JP5861514B2 - Inkjet recording device - Google Patents

Description

  The present invention relates to an ink jet recording apparatus, and more particularly, to an ink jet recording apparatus capable of ejecting dots having different droplet sizes for each pixel period with a simple driving circuit configuration without unnecessarily increasing a driving period.

  An ink jet recording apparatus that records an image using an ink jet recording head (hereinafter referred to as a recording head) that discharges minute ink droplets from a nozzle applies a pressure to ink in a pressure chamber by operating a pressure generating means. Ink droplets are ejected from the ink and landed on a recording medium such as recording paper. As the pressure generating means, a piezoelectric material such as PZT, which is generally an electric / mechanical conversion means, is used. The piezoelectric material is sandwiched between two drive electrodes, and is driven to deform by applying a drive waveform of a predetermined voltage between these drive electrodes. By this deformation drive, the volume in the pressure chamber is expanded or contracted, A pressure for ejection is applied to the ink in the pressure chamber.

  Such an ink jet recording system has a relatively simple configuration and enables high-precision image recording, and has been rapidly developed in a wide range of fields from home use to industrial use. Various improvement proposals have been made especially for high speed and high image quality, and while there is a high demand for high-speed printing with a recording head, such as one-pass printing using a line head, the gradation of printed images is improved. There is also a desire to achieve even higher image quality by doing so.

  As a conventional technique relating to this gradation, an ink jet recording apparatus is known in which multiple gradations can be expressed by selecting dots having different droplet sizes within one pixel period (Patent Documents 1 and 2). .

  In Patent Document 1, as shown in FIG. 13, different dedicated drive waveforms are prepared for each droplet size, and these are used properly in one pixel period T according to a desired droplet size to be ejected. I am doing so. In the figure, (a) is a drive waveform used when ejecting small dots, (b) is a drive waveform used when ejecting medium dots, and (c) is ejected large dots. It is a drive waveform used in the case.

  Further, for example, as shown in FIG. 14, Patent Document 2 prepares a drive waveform in which a plurality of types of waveforms having different shapes are sequentially generated in a predetermined order for each pixel period T, and is desired to be discharged. Depending on the desired droplet size, by selecting the part used for ejection (the part that turns on the switch circuit) from among the drive waveforms in which multiple types of waveforms are arranged, dots of different sizes can be selected. It is arranged so that it can be decided. For example, (a) in the figure shows the entire drive waveform generated within one pixel period T (sections Ta to Tf), and (b) shows only the waveform portions of sections Ta and Te are turned on. Thus, a small dot is formed, (c) forms a medium dot by turning on only the waveform portion of the section Tc, and (d) forms a large dot by turning on only the waveform portion of the section Tf. I have to.

JP 2011-5815 A JP 2001-205826 A

  In Patent Document 1, there is a problem that a load on the drive circuit is heavy because a dedicated drive waveform that differs depending on the droplet size is required individually.

  On the other hand, in Patent Document 2, the common drive waveform shown in FIG. 14A can be used even with different droplet sizes. However, when ink droplets are actually ejected, the entire drive waveform within one pixel period T is used. Only a part of is used. For this reason, the time of the waveform portion that is not used is wasted, and the drive cycle is lengthened accordingly, which is a serious problem in high-speed printing.

  Accordingly, the present invention selects different drive waveforms from a plurality of types of drive waveforms having different shapes for the two drive electrodes for operating the pressure generating means at predetermined time intervals within one pixel period. By using the differential waveform and operating the pressure generating means, dots having different sizes for each pixel period are ejected with a simple driving circuit configuration without unnecessarily increasing the driving period. It is an object of the present invention to provide an inkjet recording apparatus that can perform the above process.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

1. A plurality of nozzles for ejecting ink droplets, a pressure chamber communicating with each of the nozzles, and a piezoelectric material sandwiched between two drive electrodes, and ejecting data and small droplets for ejecting large droplets from the nozzles Based on each of a plurality of ejection data including ejection data to be ejected, a drive waveform is applied to each of the driving electrodes to change the volume of the pressure chamber, and the ink in the pressure chamber is changed to the nozzle A recording head having pressure generating means to be discharged from,
In an inkjet recording apparatus comprising a drive circuit that generates the drive waveform,
The drive waveform includes a first drive waveform composed of a non-GND waveform, a second drive waveform composed of a non-GND waveform different from the first drive waveform, and a third drive waveform composed of a GND waveform. At the same time, the driving voltage V1 of the first driving waveform and the driving voltage V2 of the second driving waveform are | V1 |> | V2 |
The drive circuit applies at least the first drive waveform and the second drive waveform of the drive waveform to one of the two drive electrodes of the pressure generating unit according to each of the ejection data. selects and applies to switched every predetermined short period of time than one pixel period, or used to apply select only the first drive waveform and the other by selecting only the second drive waveform applied By doing so, a large droplet waveform or a small droplet waveform is generated by the differential waveform between the two drive electrodes to operate the pressure generating means, and the large droplet and the small droplet are discharged from the same nozzle. out divided inkjet recording apparatus characterized Rukoto.

2. The drive circuit corresponds to first storage means for storing discharge data, and the first drive waveform, the second drive waveform, and the third drive waveform for operating the discharge data and the pressure generating means. 2. The ink jet recording apparatus according to claim 1, further comprising a second storage unit that stores information defining a relationship with the drive pattern.

3. 3. The ink jet recording apparatus according to claim 2, wherein the second storage means is rewritable.

4). 4. The ink jet recording apparatus according to 1, 2, or 3, wherein each of the first drive waveform and the second drive waveform is a rectangular wave.

5. The recording head has a common partition made of a piezoelectric material between the adjacent pressure chambers, the drive electrode is formed on the partition surface facing the pressure chamber, and shearing is performed by shearing the partition as pressure generating means. 5. The ink jet recording apparatus according to any one of 1 to 4, which is a mode type recording head.

6). The drive circuit divides all the pressure chambers into a plurality of groups with three adjacent pressure chambers as one set, and shear-transforms the partition so as to sequentially drive the three pressure chambers in each set in a time-sharing manner. 6. The inkjet recording apparatus as described in 5 above.

  According to the present invention, separate drive waveforms are selected from a plurality of types of drive waveforms having different shapes for the two drive electrodes for operating the pressure generating means at every predetermined time within one pixel period. By using the differential waveform and operating the pressure generating means, dots having different sizes for each pixel period are ejected with a simple driving circuit configuration without unnecessarily increasing the driving period. An ink jet recording apparatus capable of performing the above can be provided.

The figure which shows schematic structure of the inkjet recording device which concerns on this invention 2A and 2B are diagrams illustrating an example of a recording head 3, in which FIG. 1A is a perspective view showing an appearance in cross section, and FIG. (A) is a large droplet waveform, (b) is a diagram showing a basic configuration of a small droplet waveform, respectively. Explanatory drawing of the ink ejection operation of the recording head when ejecting large droplets and small droplets The figure which shows the case where a large droplet is discharged using a differential waveform The figure which shows the case where a small droplet is discharged using a difference waveform Explanatory drawing of discharge operation at the time of 3 cycle drive Explanatory drawing of discharge operation at the time of 3 cycle drive Explanatory drawing of discharge operation at the time of 3 cycle drive Timing chart of drive waveform applied during 3-cycle drive The figure explaining the internal structure of a drive signal generation part The figure which shows an example of the conversion table of image data and drive waveform pattern data Diagram showing conventional drive waveforms Diagram showing conventional drive waveforms

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an ink jet recording apparatus according to the present invention.

  In the ink jet recording apparatus 1, the recording medium P is sandwiched between the transport roller pair 22 of the transport mechanism 2 and further transported in the Y direction (sub-scanning direction) by the transport roller 21 that is rotationally driven by the transport motor 23. It has become.

  The recording head 3 is provided between the transport roller 21 and the transport roller pair 22 so as to face the recording surface PS of the recording medium P. This recording head 3 is shown in the drawing X substantially perpendicular to the conveyance direction (sub-scanning direction) of the recording medium P by a driving means (not shown) along the guide rail 4 spanned across the width direction of the recording medium P. The flexible cable 6 is mounted on a carriage 5 provided so as to be capable of reciprocating along the −X ′ direction (main scanning direction) with the nozzle surface facing the recording surface PS of the recording medium P. And is electrically connected to a drive signal generator 100 (see FIG. 4) provided in a drive circuit described later.

  The recording head 3 scans and moves the recording surface PS of the recording medium P in the XX ′ direction as the carriage 5 moves in the main scanning direction, and ejects ink droplets from the nozzles during the scanning movement. A desired inkjet image is recorded.

  2A and 2B are diagrams illustrating an example of the recording head 3, in which FIG. 2A is a perspective view showing an external appearance in cross section, and FIG. 2B is a cross-sectional view seen from the side.

  In the recording head 3, 30 is a channel substrate. On the channel substrate 30, a large number of narrow groove-like channels 31 and partition walls 32 are arranged in parallel so as to be alternately arranged. A cover substrate 33 is provided on the upper surface of the channel substrate 30 so as to block all the channels 31 above. A nozzle plate 34 is bonded to the end surfaces of the channel substrate 30 and the cover substrate 33, and a nozzle surface is formed by the surface of the nozzle plate 34. One end of each channel 31 communicates with the outside through a nozzle 34 a formed on the nozzle plate 34.

  The other end of each channel 31 gradually becomes a shallow groove with respect to the channel substrate 30, and communicates with a common flow path 33 a common to each channel 31 formed in the cover substrate 33. The common flow path 33 a is further closed by a plate 35, and ink is supplied from the ink supply pipe 35 b into the common flow path 33 a and each channel 31 through an ink supply port 35 a formed in the plate 35.

  Each partition wall 32 is made of a piezoelectric material such as PZT which is an electrical / mechanical conversion means. Here, the upper wall portion 32a and the lower wall portion 32b are both formed of a polarized piezoelectric material, and the polarization direction is indicated by the upper wall portion 32a and the lower wall portion 32b (indicated by arrows in FIG. 2B). However, the portion formed by the polarized piezoelectric material may be only the portion indicated by reference numeral 32 a, and may be at least a part of the partition wall 32. The partition walls 32 are arranged in parallel with the channels 31. Accordingly, one partition 32 is shared by the adjacent channels 31 and 31.

  In each channel 31, drive electrodes (not shown in FIG. 2) are formed from the wall surfaces of both partition walls 32 to the bottom surface of the channel 31, and both drive electrodes sandwiching the partition walls 32 are described later. When a driving pulse having a predetermined voltage is applied from a driving signal generator provided in the driving circuit, the partition wall 32 made of a piezoelectric material is bent and deformed at the boundary between the upper wall portion 32a and the lower wall portion 32b. . Due to the bending deformation of the partition wall 32, a pressure wave is generated in the channel 31, and a pressure for ejecting from the nozzle 34 a is applied to the ink in the channel 31. Therefore, the recording head 3 includes the channel 31 surrounded by the channel substrate 30, the cover substrate 33, and the nozzle plate 34 to form a pressure chamber according to the present invention. The present invention is a shear mode type recording head in which the pressure generating means in the invention is configured and the partition wall 32 is subjected to shear deformation to eject ink droplets.

  A drive signal generator provided in a drive circuit electrically connected to the recording head 3 via the flexible cable 6 generates a drive waveform to be applied within one pixel period in order to eject ink droplets. Here, large droplets (large dots) and small droplets (small dots) are ejected from the same nozzle 34a to generate a drive waveform for expressing gradation.

  An example of driving waveforms for ejecting these large droplets and small droplets will be described with reference to FIG. FIG. 3A shows a basic configuration of a large droplet waveform for discharging a large droplet, and FIG. 3B shows a basic configuration of a small droplet waveform for discharging a small droplet. The ink ejection operation of the recording head 3 when the large droplet waveform and the small droplet waveform are applied will be described with reference to FIG. FIG. 4 shows a part of a cross section obtained by cutting the recording head 3 in a direction orthogonal to the length direction of the channel.

  The large droplet waveform PA includes a rectangular wave including a 3AL-width expansion pulse Pa1 that expands the channel volume and a 2AL-width contraction pulse Pa2 that contracts the channel volume.

  Here, AL (Acoustic Length) means 1/2 of the acoustic resonance period of the pressure wave in the channel. AL measures the speed of the ink droplet ejected when a rectangular wave drive pulse is applied to the drive electrode, and changes the rectangular wave pulse width while keeping the rectangular wave voltage value constant. It is obtained as the pulse width that maximizes the flight speed.

  A pulse is a rectangular wave having a constant voltage peak value. When 0V is 0% and a peak voltage is 100%, the pulse width is 10% of the voltage from 0V and the peak voltage. It is defined as the time between 10% of the falling edge.

  Furthermore, a rectangular wave refers to a waveform in which both the rise time and fall time between 10% and 90% of the voltage are within ½, preferably within ¼ of AL.

  In the present invention, it is preferable that the drive waveforms for ejecting the large droplets and the small droplets are both rectangular waves. In particular, in the shear mode type recording head 3 shown in the present embodiment, ink droplets are ejected from the nozzles 34a using the resonance of the pressure wave generated in the channel 31, so that the ink droplets can be more efficiently used by using a rectangular wave. Can be discharged.

  Further, since the shear mode type recording head 3 has a fast meniscus response to the application of a drive waveform consisting of a rectangular wave, the drive voltage can be kept low. In general, a voltage is always applied to the recording head 3 regardless of whether it is ejected or not. Therefore, a low driving voltage is important for suppressing heat generation of the head and ejecting ink droplets stably.

  Furthermore, since the rectangular wave can be easily generated by using a simple digital circuit, there is an advantage that the circuit configuration can be simplified as compared with the case of using a trapezoidal wave having a gradient wave.

  The expansion pulse Pa1 in the large droplet waveform PA is a pulse for applying a predetermined positive drive voltage + Von to the drive electrode 36B facing the channel 31B for ejecting ink droplets. As shown in FIG. 4A, when no drive pulse is applied to any of the drive electrodes 36A, 36B, 36C in the adjacent channels 31A, 31B, 31C, any of the partition walls 32A, 32B, 32C, 32D However, when the drive electrodes 36A and 36C are grounded and the expansion pulse Pa1 is applied to the drive electrode 36B in this neutral state, they are perpendicular to the polarization direction of the piezoelectric material constituting the partition walls 32B and 32C. Electric field in any direction is generated. As a result, both the partition walls 32B and 32C are deformed at the joint surfaces of the upper wall portion 32a and the lower wall portion 32b, respectively, and the partition walls 32B and 32C are bent and deformed outward as shown in FIG. 4B. Then, the volume of the channel 31B is expanded. Due to this bending deformation, a negative pressure wave is generated in the channel 31B, and ink flows.

  Since the pressure in the channel 31B is reversed every 1AL, the channel 31B after the 3AL has a positive pressure, and the contraction pulse Pa2 is applied to the drive electrode 36B at this timing.

  The contraction pulse Pa2 is a pulse for applying the negative drive voltage −Voff without any rest period following the end of the application of the expansion pulse Pa1. When this drive voltage -Voff is applied to the drive electrode 36B in succession to the expansion pulse Pa1, the movement of the partition walls 32B and 32C at this time is illustrated at once from the state of being deformed outward as shown in FIG. 4B. As shown in 4 (c), it is deformed inward. As a result, by adding the positive pressure due to the falling of the expansion pulse Pa1, a larger pressure is applied in the channel 31B, and a relatively large ink droplet is ejected from the nozzle. The contraction pulse Pa2 is returned to 0 potential after 2AL, and the residual pressure wave is canceled by the deformation of the partition walls 32B and 32C returning to the neutral state in FIG.

  On the other hand, the small droplet waveform PB is composed of a rectangular wave including a 1AL-width expansion pulse Pb1 that expands the volume of the channel and a 1AL-width contraction pulse Pb2 that contracts the volume of the channel. Between the pulse Pb2, there is a rest period Pb3 in which 0 potential that does not deform the partition is continued with a width of 1AL.

  The expansion pulse Pb1 in the small droplet waveform PB is a pulse for applying a predetermined positive drive voltage + Von to the drive electrode 36B facing the channel 31B for ejecting ink droplets. In the neutral state shown in FIG. 4A, when the drive electrodes 36A and 36C are grounded and the expansion pulse Pb1 is applied to the drive electrode 36B, the partition walls 32B and 32C are, as shown in FIG. Bending and deforming toward each other, the volume of the channel 31B is expanded. Due to this bending deformation, a negative pressure wave is generated in the channel 31B, and ink flows.

  Since the pressure in the channel 31B is reversed to a positive pressure after 1 AL, when the drive electrode 36B is returned to 0 potential at this timing, the partition walls 32B and 32C are moved from the enlarged position shown in FIG. 4B to FIG. 4A. Returning to the neutral state shown, a pressure for discharge is applied in the channel 31B. Since the partition walls 32B and 32C only return to the neutral state at this time, only a small pressure is applied to the channel 31B as compared with the large droplet waveform PA. As a result, a relatively small ink droplet is ejected from the nozzle.

  The contraction pulse Pb2 is a pulse for applying a negative drive voltage −Voff after a pause period Pb3 in which the state of 0 potential continues for 1 AL after the end of the application of the expansion pulse Pb1. At the time when the 1AL rest period Pb3 ends after the application of the expansion pulse Pb1, the partition walls 32B and 32C remain in the neutral state as shown in FIG. 4A, but the pressure in the channel 31B is a negative pressure. It has become. When the contraction pulse Pb2 is applied to the drive electrode 36B at this timing, the partition walls 32B and 32C are deformed inward, so that a positive pressure is applied to the channel 31B in the negative pressure state. As a result, the residual pressure wave in the channel 31 is canceled.

  In the above description, the pulse width of the expansion pulse Pa1 in the large droplet waveform PA is 3AL, but it may be in the range of 2.8AL to 3.4AL. Further, the pulse width of the expansion pulse Pb1 in the small droplet waveform PB is not limited to 1AL, and may be in the range of 0.8AL to 1.2AL.

  Further, as shown in the present embodiment, the pulse width of the contraction pulse Pa2 of the large droplet waveform PA is set to 2AL, and the pulse widths of the expansion pulse Pb1, the pause period Pb3, and the contraction pulse Pb2 of the small droplet waveform PB are respectively set. By setting 1AL, the pulse width of the entire drive waveform can be reduced. Since the pulse width can be reduced, the drive waveform can be applied in such a short period, which is a more preferable aspect for high-speed printing.

  The driving voltage + Von of the expansion pulse Pa1 of the large droplet waveform PA is the same voltage as the driving voltage + Von of the expansion pulse Pb1 of the small droplet waveform PB, and the driving voltage −Voff of the contraction pulse Pa2 of the large droplet waveform PA. Is preferably the same voltage as the drive voltage −Voff of the contraction pulse Pb2 of the small droplet waveform PB. Since only one power source is required for the large droplet and small droplet drive signals, the configuration of the drive circuit and the control circuit can be simplified.

  By the way, the deformation of the partition wall 32 constituting the pressure generating means is caused by a voltage difference between two drive electrodes provided so as to sandwich the wall. For example, in the case of the partition wall 32B shown in FIG. 4, a drive waveform composed of a positive voltage (+ Von) and a negative voltage (−Voff) shown in FIG. 3 is applied to one drive electrode 36B, and the other drive electrode 36A is grounded. A voltage difference is generated. In the present invention, different drive waveforms are applied to the two drive electrodes provided so as to sandwich the partition wall 32 in this manner, and the difference waveform of the drive waveforms is used actively to drive.

  In this case, as shown in FIG. 3A, the large droplet waveform PA whose polarity is switched between positive and negative is for the discharge channel of the positive voltage (+ Von) applied to the drive electrode in the discharge channel for discharging the ink droplet. The waveform PA1 (FIG. 5A) and a non-ejection waveform PA2 (FIG. 5B) having a positive voltage (+ Voff) applied to the drive electrodes in the adjacent non-ejection channels are unipolar. It can be divided into waveform components.

  For example, when the channel 31B in FIG. 4 is used as the ejection channel, the ejection electrode waveform PA1 including only the expansion pulse Pa1 having the positive voltage (+ Von) shown in FIG. Is applied to the drive electrodes 36A and 36C facing the adjacent channels 31A and 31C, which are non-ejection channels, and include only the contraction pulse Pa2 having the positive voltage (+ Voff) shown in FIG. When the waveform PA2 is applied, the partition walls 32B and 32C apply the drive waveform PA of FIG. 3A only to the drive electrode 36B by the differential waveform between the drive electrodes 36A and 36B and the drive electrodes 36B and 36C on both surfaces thereof. Then, large droplets can be ejected by being deformed and driven in exactly the same way as when the drive electrodes 36A and 36C are grounded.

  Similarly, as shown in FIG. 3B, the small droplet waveform PB whose polarity switches between positive and negative is a discharge channel of a positive voltage (+ Von) applied to the drive electrode in the discharge channel for discharging the ink droplet. A single polarity of the waveform PB1 (FIG. 6A) and the non-ejection waveform PB2 (FIG. 6B) of the positive voltage (+ Voff) applied to the drive electrodes in the adjacent non-ejection channels on both sides thereof It can be divided into waveform components.

  Similarly, when the small droplet waveform PB is applied to the channel 31B, the drive electrode 36B facing the channel 31B includes only the expansion pulse Pb1 that is the positive voltage (+ Von) shown in FIG. Only the contraction pulse Pb2 that is the positive voltage (+ Voff) shown in FIG. 6B is applied to the drive electrodes 36A and 36C that are applied to the discharge channel waveform PB1 and face the adjacent channels 31A and 31C that are non-discharge channels. 3B is applied to only the drive electrode 36B by the differential waveform between the drive electrodes 36A and 36B and the drive electrodes 36B and 36C on both surfaces thereof. Small droplets can be ejected by applying a driving waveform PB and driving the deformation in exactly the same way as when the driving electrodes 36A and 36C are grounded.

  In this way, the partition wall 32 constituting the pressure generating means is deformed by utilizing the differential waveform when different drive waveforms are applied, so that the drive waveform for discharging large droplets and small droplets can be obtained. Here, it can be constituted only by positive voltages (+ Von, + Voff), and the drive circuit can be simplified.

  When driving the recording head 3 in which a plurality of channels 31 separated by the partition walls 32 constituting the pressure generating means are driven in parallel as in the present embodiment, when the partition walls 32 of one channel 31 perform an ejection operation, The adjacent channels 31 are affected. In this case, every other channel, for example, the channels 31A and 31C in FIG. 4 is a non-ejection dedicated channel (also referred to as a dummy channel or an air channel) that does not eject ink droplets, and the independent driving method in which ejection is always performed from the channel 31B. However, in general, all three channels 31 are divided into a plurality of groups, with three adjacent channels among a plurality of channels 31 as one set, and the three channels in each group are sequentially driven in a time-sharing manner. A three-cycle driving method is performed.

  Therefore, the operation for ejecting large droplets and small droplets using the differential waveform will be described with reference to FIGS.

  In the recording head 3 in the case of performing the 3-cycle driving method, every other channel 31 is grouped into one group, and all the channels 31 are grouped into three groups of A, B, and C (this is A phase, B phase, Of these, nine channels 31 of A1, B1, C1, A2, B2, C2, A3, B3, and C3 that are adjacent to each other will be described here. FIG. 10 shows a timing chart of drive waveforms applied to the drive electrodes (not shown in FIGS. 7 to 9) in the A-phase, B-phase, and C-phase channels 31 at this time. Here, the large droplet waveform PA shown in FIG. 3A is generated using the differential waveform shown in FIG. 5 to eject the large droplet, and the small droplet waveform PB shown in FIG. It is assumed that a small droplet is ejected by using the differential waveform shown in FIG. 6, and the ink is in the order of B phase channel (large droplet) → C phase channel (small droplet) → A phase channel (large droplet). The case where a droplet is discharged is shown.

  The drive waveforms for ejecting large droplets and small droplets by the differential waveform are selected by selecting one of the PLSTM0 waveform, PLSTM1 waveform, and PLSTM2 waveform shown in FIG. Created every time. The PLSTM0 waveform is a GND waveform that maintains a zero potential for grounding, and is the third drive waveform in the present invention. The PLSTM1 waveform is a waveform that repeats the 3AL + Von waveform corresponding to the expansion pulse Pa1 of the large droplet waveform PA with a 3AL rest period, and is the first driving waveform in the present invention. The PLSTM2 waveform is a waveform that repeats a 2AL + Voff waveform corresponding to the contraction pulse Pa2 of the large droplet waveform PA with a 4AL rest period, and is the second driving waveform in the present invention. This PLSTM2 waveform is repeated at the rising timing in synchronization with the falling edge of the PLSTM1 waveform, and ejection from each of the A-phase, B-phase, and C-phase channels is 6AL (AL = 3.0 μs) within one pixel period T. ) Is performed sequentially in the period of ().

  The PLSTM2 waveform is set so that the timing of the rising edge of the pulse is shifted by 3AL from the rising edge of the pulse of the PLSTM1 waveform and rises in synchronization with the falling edge of the pulse of the PLSTM1 waveform.

  The driving voltage V1 having the PLSTM1 waveform and the driving voltage V2 having the PLSTM waveform are | V1 |> | V2 |. Accordingly, since an element having a lower tolerance than V1 can be used for V2, a circuit for generating V1 can be made inexpensive and small.

  The pulse division signal is a timing signal for generating the small droplet waveform PB by dividing the PLSTM1 waveform and the PLSTM2 waveform, and in the rising period of the pulse selection gate signal corresponding to one pixel period T, the pulse selection gate The first and second pulse division signals d2 and d3 that rise at 1AL intervals from the first pulse division signal d1 that rises in synchronization with the rising edge of the signal and rises 2AL after the rising edge of the third pulse division signal d3 It is composed of a total of four signals including the fourth pulse division signal d4.

  FIG. 7 shows an ejection operation when ejecting a large droplet from the B-phase channel. First, within the one-pixel period T of the B-phase channel, the first pulse from the neutral state in FIG. A phase channels (A1, A2, A3) and C phase channels (C1, C2, C3) which are non-ejection channels in synchronization with the rising edge of the divided signal d1 (rising edge of the pulse selection gate signal of the B phase channel) In addition, as shown in FIG. 10, the PLSTM2 waveform is selected and applied, and the PLSTM1 waveform is selected and applied to the B-phase channels (B1, B2, B3) serving as the ejection channels. As a result, the expansion pulse Pa1 of the large droplet waveform PA is generated by the difference waveform between the PLSTM1 waveform and the PLSTM2 waveform, and both the partition walls are deformed outward as shown in FIG. The volume of swells.

  After the passage of 3AL, the PLSTM2 waveform applied to the A phase channel and the C phase channel rises at the falling edge timing of the expansion pulse Pa1 included in the PLSTM1 waveform, and the large droplet waveform PA appears in these A phase channel and C phase channel. A 2AL contraction pulse Pa2 is applied. As a result, the contraction pulse Pa2 of the large droplet waveform PA is generated by the differential waveform between the PLSTM1 waveform and the PLSTM2 waveform, and both the partition walls are deformed inward as shown in FIG. The volume of the liquid droplets shrinks all at once, and a large droplet is discharged from each nozzle of the B phase channel.

  After the contraction pulse Pa2 continues for 2AL, the A-phase channel, the B-phase channel, and the C-phase channel become 0 potential, and all the channels return to the neutral state as shown in FIG. 7A to cancel the residual pressure wave.

  Next, FIG. 8 shows an ejection operation when ejecting a small droplet from the C phase, and the first pulse from the neutral state in FIG. 8A within one pixel period T of the C phase channel. In synchronization with the rising edge of the divided signal d1 (the rising edge of the pulse selection gate signal of the C-phase channel), the PLSTM2 waveform is selected as shown in FIG. In addition to the application, the PLSTM0 waveform is selected and applied to the C-phase channel serving as the ejection channel. At this time, since all waveforms are at 0 potential, all the channels remain in the neutral state of FIG.

  Next, the PLSTM1 waveform is selected and applied only to the C phase channel in synchronization with the rising edge of the second pulse division signal d2. As a result, the differential waveform between the PLSTM0 waveform and the PLSTM1 waveform causes the B-phase channel to be deformed toward the outside as shown in FIG. 8B, and the volume in the channel expands.

  After the application of the PLSTM1 waveform to the C-phase channel is continued for 1 AL, when the PLSTM0 waveform is selected again for the C-phase channel at the timing of the rising edge of the third pulse division signal d3, all channels are shown in FIG. Return to neutral state. As a result, the differential waveform of the PLSTM0 waveform, the PLSTM1 waveform, and the PLSTM2 waveform functions in the same manner as the expansion pulse Pb1 of the small droplet waveform PB, and in the C-phase channel, both the partitions are directed from the expanded state to the neutral state in FIG. Therefore, a small droplet is ejected from each nozzle of the C-phase channel.

  When 1AL has elapsed from the falling edge of the PLSTM1 waveform applied to the C-phase channel, the PLSTM2 waveform applied to the A-phase channel and the B-phase channel rises. As a result, the differential waveform between the PLSTM1 waveform and the PLSTM2 waveform functions in the same manner as the contraction pulse Pb2 of the small droplet waveform PB, and both partition walls of the C-phase channel are changed from the neutral state of FIG. 8A to FIG. 8C. So that it shrinks inward.

  Thereafter, when the PLSTM2 waveform is selected and applied to the C-phase channel in synchronization with the rising edge of the fourth pulse division signal d4, the positive voltage + Voff of the same voltage is applied to the A-phase channel, the B-phase channel, and the C-phase channel. Since it is in the applied state, there is no voltage difference across all partitions, and all channels return to the neutral state of FIG.

  FIG. 9 shows an ejection operation when ejecting a large droplet from the A-phase channel, and the first pulse division signal from the neutral state in FIG. 9A within one pixel period T of the A-phase channel. In synchronization with the rising edge of d1 (the rising edge of the A-phase channel pulse selection gate signal), the PLSTM2 waveform is selected and applied to the B-phase channel and C-phase channel, which are non-ejection channels, as shown in FIG. At the same time, the PLSTM1 waveform is selected and applied to the A-phase channel serving as the ejection channel. As a result, the expansion pulse Pa1 of the large droplet waveform PA is generated by the differential waveform between the PLSTM1 waveform and the PLSTM2 waveform, and the A-phase channel is deformed toward the outside as shown in FIG. The volume of swells.

  After the passage of 3AL, the PLSTM2 waveform applied to the B-phase channel and the C-phase channel rises at the falling edge timing of the expansion pulse Pa1 included in the PLSTM1 waveform, and the large droplet waveform PA appears in these B-phase channel and C-phase channel. A 2AL contraction pulse Pa2 is applied. As a result, the contraction pulse Pa2 of the large droplet waveform PA is generated by the difference waveform between the PLSTM1 waveform and the PLSTM2 waveform, and both the partition walls are deformed inward as shown in FIG. The volume of the liquid droplets shrinks all at once, and a large droplet is ejected from each nozzle of the A-phase channel.

 After the contraction pulse Pa2 continues for 2AL, the A-phase channel, the B-phase channel, and the C-phase channel become 0 potential, and all the channels return to the neutral state as shown in FIG. 9A to cancel the residual pressure wave.

  The above three-cycle driving is a case where large droplets are ejected from the A phase and the B phase, and small droplets are ejected from the C phase, respectively. However, in any of the phases A to C, the PLSTM0 waveform, the PLSTM1 waveform, and the PLSTM2 waveform It will be easily understood that large droplets and small droplets can be arbitrarily arranged for each pixel period T by appropriately selecting.

  That is, according to the present invention, even when large droplets and small droplets are separated from the same nozzle, three types of driving waveforms of PLSTM0 waveform, PLSTM1 waveform and PLSTM2 waveform are used in common, and within one pixel period T. When a large droplet is ejected at predetermined time intervals divided by the first pulse division signal d1 to the fourth pulse division signal d4 in FIG. 1, the PLSTM1 waveform is selected and adjacent to the drive electrode of the ejection channel. The PLSTM2 waveform is selected as the drive electrode for the non-ejection channel, and when ejecting small droplets, the PLSTM0 waveform, the PLSTM1 waveform, and the PLSTM2 waveform are selected as appropriate for the ejection channel drive electrode, and the PLSTM2 is selected for the non-ejection channel. By selecting the waveform, the partition wall 32 can be operated by the differential waveform between the two drive electrodes.

  In addition, according to the present invention, since only three types of driving waveforms that are common to large droplets and small droplets are necessary, the driving circuit can be simplified.

  In addition, since either a large droplet waveform or a small droplet waveform is generated within one pixel period T, a time for a waveform that is not used within one pixel period T is provided as in the prior art. There is no need to keep it. For this reason, the driving cycle does not become unnecessarily long, and an image with improved gradation can be printed at high speed.

  Next, a drive signal generator that performs control for appropriately separating three types of drive waveforms at predetermined time intervals within one pixel period T and sorting large droplets and small droplets using the differential waveform. An example of the internal configuration of 100 will be described with reference to FIG.

  A drive signal generation unit 100 shown in FIG. 11 shows a case of a 128-channel drive IC, and a first latch circuit 102A of 2 bits × 128 channels (nozzles) as a first latch means, a second latch. 2 bit × 128 channel (nozzle) second latch circuit 102B as the means, shift register 101 as the first storage means for outputting image data (ejection data) to the first latch circuit 102A, based on the ejection data. A gray scale controller 103 for driving the partition wall 32 as pressure generating means for discharging large droplets or small droplets, an output pattern register 104 as second storage means, a three-phase buffer amplifier 105, and the like. Composed. A register such as the output pattern register 104 is preferably used as the second storage means.

  In this embodiment, a configuration corresponding to 2 bits is used to process image data composed of three gradations (0 = non-discharge, 1 = small droplet, 2 = large droplet) of 0 to 2 per pixel. ing. In synchronization with a transfer clock DCLK input from a control circuit (not shown), image data of 2 bits per pixel is transferred to the shift register 101 serially in units of pixels. This transfer timing is common among the nozzle rows.

  The shift register 101 has a capacity capable of storing image data of a number of pixels corresponding to one ejection of 128 nozzles. By connecting two shift registers 101, in this embodiment, image data for 256 pixels corresponding to nozzles for one column arranged in the sub-scanning direction is stored. When the carriage on which the recording head 3 is mounted reaches a predetermined position, the control circuit outputs a LAT1 signal that is a first trigger signal for instructing the latch timing, and the first latch circuit 102A outputs this LAT1 signal. When received, the image data output from the shift register 101 in parallel is latched.

  When the carriage on which the recording head 3 is mounted reaches a predetermined position, the control circuit outputs a LAT2 signal that is a second trigger signal for instructing the latch timing, and the second latch circuit 102B outputs the LAT2 signal. When received, the image data output in parallel from the first latch circuit 102A is latched.

  As described above, the image data output from the shift register 101 is latched by the second latch circuit 102B via the first latch circuit 102A.

  When the recording head 3 reaches a position suitable for recording, the control circuit outputs a TRGIN signal for starting ink ejection, and when the second latch circuit 102B receives this TRGIN signal, the second latch circuit The image data latched in 102B is output to the gray scale controller 103.

  As described above, by providing two latch means, the data transfer speed is not increased more than necessary, and the recording speed is not lowered. Data transfer can be performed simultaneously, and data transfer trigger processing can be performed efficiently. Further, the configuration of the control system can be simplified, and the landing position of the droplet for each nozzle row can be adjusted more finely than the pixel pitch.

  Three types of drive waveforms (three types of PLSTM0, PLSTM1, and PLSTM2 described above) are input to the gray scale controller 103 through an input terminal from a circuit (not shown) that generates a drive waveform.

  In addition, the gray scale controller 103 shows all channels corresponding to 256 nozzles in FIG. 10 according to the selection signals (the aforementioned pulse selection gate signals) STB-1, 2, and 3 supplied from the input terminals. As described above, the control unit is configured to be divided into three sets of the A phase, the B phase, and the C phase, and to sequentially divide and drive the partition walls, which are the corresponding pressure generating units, by three-cycle driving. In STB-1, the A phase is selected, in STB-2 the B phase is selected, in STB-3 the C phase is selected, and ink droplets are sequentially ejected from the corresponding nozzles.

  Further, the gray scale controller 103 has count means 106 that counts what number waveform in the drive waveform pattern is output. The GSC (gray scale count) that is the count value of the count means 106 is set to 0 to 0. Count to 4.

  Further, the gray scale controller 103 outputs an output pattern that stores a conversion table that is information defining the relationship between image data that is ejection data and drive waveform pattern data corresponding to a drive waveform that drives a partition wall that is pressure generating means. A register 104 is included. In this embodiment, drive waveform pattern data corresponding to a plurality of drive waveforms is shown.

  First, the counting means is reset by the input LOAD signal. For example, STB-1 is selected, and an A-phase channel (nozzle) is selected. The drive waveform pattern data is determined from the image data corresponding to each channel of the A phase by the conversion table stored in the output pattern register 104. Note that predetermined drive waveform pattern data is selected for the B-phase and C-phase channels that are not driven. GSC, which is the count value of the counting means, is incremented by 1 from 0 to determine the drive waveform to be output. The drive waveform is selected from three types of drive waveforms, PLSTM0 waveform, PLSTM1 waveform, and PLSTM2 waveform, according to the image data and the count value of the counting means. These waveforms are selected by the switching means (not shown) from the above-mentioned three types of drive waveforms and output in synchronization with the input GSCLK timing signal.

  The three-phase buffer amplifier 105 shifts the level of the drive waveform output from the gray scale controller 103 to the power supply voltage necessary for driving the partition wall. At this time, the drive voltage + Von of the drive waveform is determined by the voltage value V1 input from the input terminal, and the drive voltage + Voff of the drive waveform is determined by the voltage value V2 input in the same manner. Are output to the corresponding partition drive electrodes, and ink droplets are ejected from the corresponding nozzles. By changing the voltage values of V1 and V2, the drive voltage can be changed to an optimum value.

  When the count value of the counting means reaches GSC = 4, it is determined that the ejection of ink droplets from the A-phase channel is completed, the counting means 106 is reset by the LOAD signal, and then the B-phase by the STB-2 signal. Is selected, and ink droplets are similarly ejected for the B phase. When the B phase is completed, ink ejection is similarly performed for the C phase. This completes the ink ejection for all the nozzles for one row, and the recording is repeated again based on the next image data.

  FIG. 12 is a diagram illustrating an example of a conversion table between image data and drive waveform pattern data.

  In the image data, three gradations are represented by gradation value 0 (non-ejection), gradation value 1 (small droplet), and gradation value 2 (large droplet).

  There are three types of drive waveform pattern data, PLSTM0 to 2 described above, and these correspond to the five states GSC = 0 to 4 of the count value of the count means described above. The drive waveform pattern data “0” indicates that PLSTM0 is selected, “1” indicates that PLSTM1 is selected, and “2” indicates that PLSTM2 is selected.

  Further, since the data is output from the bit located later, for example, in the case of the gradation value 1 in the table of FIG. 12, drive waveform pattern data (2, 0, 1, 0, 0) is selected, Drive waveform pattern data (0, 0, 1, 0, 2) is output. The output drive waveform pattern corresponds to the count value GSC = 0 to 4 described above. In this case, the count value of the count means is 0 when GSC = 0, and when GSC = 1. When 0 and GSC = 2, 1 is output as the selected drive waveform data, 1 when GSC = 3, and 2 when GSC = 4.

  Note that GSC = 1 to 4 corresponds to the aforementioned pulse division signals d1 to d4.

  As described above, the STB signal divides a channel corresponding to 256 nozzles into three phases A, B, and C according to three divided signals STB-1, STB-2, and STB-3, Corresponding partition walls are sequentially divided and driven.

  For example, in the example of the timing chart shown in FIG. 10, first, n = 2 and the partition wall of the B-phase channel is driven to eject a large droplet having a gradation value of 2. In this case, the B-phase channel In the table of FIG. 12, drive waveform pattern data of (1, 1, 1, 1, 0) is selected and (0, 1, 1, 1, 1) is output. On the other hand, for the A-phase and C-phase channels corresponding to n = 1, 3, (2, 2, 2, 2, 0) drive waveform pattern data is selected regardless of the image data, and (0, 2, 2, 2, 2) is output.

  As a result, as shown in FIG. 10, the B-phase channel, which is an ejection channel, is a non-ejection channel in which only PLSTM1 is selected in each period divided by the pulse division signals d1 to d4 in one pixel period T. For the A-phase and C-phase channels, only PLSTM2 is selected in each period divided by the pulse division signals d1 to d4 in one pixel period T.

  Next, at n = 3, the C-phase channel partition is driven to discharge a small droplet having a gradation value of 1. In this case, the C-phase channel has (2, 0) in the table of FIG. , 1, 0, 0) is selected and (0, 0, 1, 2, 2) is output. On the other hand, for the A-phase and B-phase channels corresponding to n = 1, 2, (2, 2, 2, 2, 0) drive waveform pattern data is selected regardless of the image data, and (0, 2, 2, 2, 2) is output.

  As a result, as shown in FIG. 10, in the C-phase channel as the ejection channel, PLSTM0 is selected in the period divided by the pulse division signal d1 in one pixel period T, and the period divided by the pulse division signal d2 PLSTM1 is selected, PLSTM0 is selected in the period divided by the pulse division signal d3, PLSTM2 is selected in the period divided by the pulse division signal d4, and the A-phase and B-phase channels that are non-ejection channels are In one pixel period T, only PLSTM2 is selected in each period divided by the pulse division signals d1 to d4.

  Next, when n = 1, the A-phase channel partition is driven to discharge a large droplet having a gradation value of 1. In this case, in the table of FIG. , 1, 1, 0) is selected and (0, 1, 1, 1, 1) is output. On the other hand, for the B-phase and C-phase channels corresponding to n = 2, 3, the drive waveform pattern data of (2, 2, 2, 2, 0) is selected regardless of the image data, and (0, 2, 2, 2, 2) is output.

  As a result, as shown in FIG. 10, the A-phase channel, which is an ejection channel, is a non-ejection channel in which only PLSTM1 is selected in each period divided by the pulse division signals d1 to d4 in one pixel period T. For the B-phase and C-phase channels, only PLSTM2 is selected in each period divided by the pulse division signals d1 to d4 in one pixel period T.

  Therefore, when the count value of the counting means is GSC = 0, the driving waveform data of 0 is selected in any of the A phase, B phase, and C phase channels, and the partition is not driven, but when GSC = 1 to 4, The partition is driven as described above according to the drive waveform data.

  Further, in the case of a recording head having 256 channels for ejecting ink, it is necessary to deform both partition walls of the two channels arranged at both ends thereof. One dummy channel that does not eject ink droplets is arranged one by one. The drive electrode of this dummy channel has (2, 2, 2, 2, 0) drive waveform pattern data as out-D. Is selected and (0, 2, 2, 2, 2) is output. As a result, the partition walls of the dummy channels are driven in accordance with the drive waveform applied to the electrodes corresponding to the image data of the channels at both ends of the 256 channels.

  Thus, the drive signal generator 100 of the drive circuit has the shift register 101 as the first storage means for storing the discharge data, the first drive waveform (PLSTM1) for operating the discharge data and the pressure generation means, and the first And an output pattern register 104 as second storage means for storing information defining the relationship with the drive patterns corresponding to the second drive waveform (PLSTM2) and the third drive waveform (PLSTM0). Thus, the drive waveform selected every predetermined time within one pixel period can be quickly switched and applied to the pressure generating means.

  The output pattern register 104 as the second storage means is preferably rewritable. The rewritable means that the contents can be changed as necessary from a control unit or the like that controls the ink jet recording apparatus (not shown), and in this way, in drive waveforms other than the drive waveforms shown in the present embodiment. In the same way, the contents of the register can be rewritten to make a similar arrangement.

1: Inkjet recording apparatus 2: Conveying mechanism 21: Conveying roller 22: Conveying roller pair 23: Conveying motor 3: Recording head 30: Channel substrate 31: Channel 32: Partition wall 32a: Upper wall portion 32b: Lower wall portion 33: Cover substrate 33a: common flow path 34: nozzle plate 34a: nozzle 35: plate 35a: ink supply port 35b: ink supply pipe 4: guide rail 5: carriage 6: flexible cable 100: drive signal generator 101: shift register (first register Storage means)
102A: first latch circuit 102B: second latch circuit 103: gray scale controller 104: output pattern register (second storage means)
105: Three-phase buffer amplifier P: Recording medium PS: Recording surface PA: Large droplet waveform Pa1: Expansion pulse Pa2: Contraction pulse PB: Small droplet waveform Pb1: Expansion pulse Pb2: Contraction pulse Pb3: Rest period

Claims (6)

A plurality of nozzles for ejecting ink droplets, a pressure chamber communicating with each of the nozzles, and a piezoelectric material sandwiched between two drive electrodes, and ejecting data and small droplets for ejecting large droplets from the nozzles Based on each of a plurality of ejection data including ejection data to be ejected, a drive waveform is applied to each of the driving electrodes to change the volume of the pressure chamber, and the ink in the pressure chamber is changed to the nozzle A recording head having pressure generating means to be discharged from,
In an inkjet recording apparatus comprising a drive circuit that generates the drive waveform,
The drive waveform includes a first drive waveform composed of a non-GND waveform, a second drive waveform composed of a non-GND waveform different from the first drive waveform, and a third drive waveform composed of a GND waveform. At the same time, the driving voltage V1 of the first driving waveform and the driving voltage V2 of the second driving waveform are | V1 |> | V2 |
The drive circuit applies at least the first drive waveform and the second drive waveform of the drive waveform to one of the two drive electrodes of the pressure generating unit according to each of the ejection data. selects and applies to switched every predetermined short period of time than one pixel period, or used to apply select only the first drive waveform and the other by selecting only the second drive waveform applied By doing so, a large droplet waveform or a small droplet waveform is generated by the differential waveform between the two drive electrodes to operate the pressure generating means, and the large droplet and the small droplet are discharged from the same nozzle. out divided inkjet recording apparatus characterized Rukoto.   The drive circuit corresponds to first storage means for storing discharge data, and the first drive waveform, the second drive waveform, and the third drive waveform for operating the discharge data and the pressure generating means. 2. The ink jet recording apparatus according to claim 1, further comprising second storage means for storing information defining a relationship with the drive pattern.   3. The ink jet recording apparatus according to claim 2, wherein the second storage means is rewritable.   4. The ink jet recording apparatus according to claim 1, wherein each of the first drive waveform and the second drive waveform is a rectangular wave.   The recording head has a common partition made of a piezoelectric material between the adjacent pressure chambers, the drive electrode is formed on the partition surface facing the pressure chamber, and shearing is performed by shearing the partition as pressure generating means. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is a mode type recording head.   The drive circuit divides all the pressure chambers into a plurality of groups with three adjacent pressure chambers as one set, and shear-transforms the partition so as to sequentially drive the three pressure chambers in each set in a time-sharing manner. 6. An ink jet recording apparatus according to claim 5, wherein

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